A mobile communication system of the LTE scheme (Release.8) defined by the 3GPP, as illustrated in FIG. 12, is configured such that when a handover process of a mobile station UE is carried out from a radio base station eNB#1 to a radio base station eNB#2, control signals involved in the handover process are sent and received between the radio base station eNB#1 and the radio base station eNB#2 via an X2 bearer that has been set between the radio base station eNB#1 and the radio base station eNB#2.
As illustrated in FIG. 12, the radio base station eNB#1 and the radio base station eNB#2 include a network layer 1 (NW L1) function, a network layer 2 (NW L2) function, an IP (Internet Protocol) layer function, and an SCTP (Stream Control Transmission Protocol) layer function as the X2 bearer functions configured to establish the X2 bearer.
In an LTE-Advanced mobile communication system, which is the communication scheme that is the next-generation of the LTE scheme, “relay nodes RN” including the same functions as a radio base station eNB can establish a connection between a mobile station UE and the radio base station eNB.
However, the conventional mobile communication system has been problematic in that there is no regulation for how handover processes of the mobile station UE are to be performed when the relay nodes RN have been connected.
Therefore, the present invention is intended to overcome the above-described problem. An object of the present invention is to provide a mobile communication system capable of also implementing handover processes by a mobile station even when relay nodes have been connected.